CSDMS 2016 annual meeting poster JuliaMoriarty
The Roles of Resuspension and Redistribution on Nutrient Cycling in the Northern Gulf of Mexico: Results From A Coupled Hydrodynamic-Sediment Transport – Biogeochemical Numerical Model
Courtney Harris, Virginia Institute of Marine Science, College of William & Mary Hayes Virginia, United States. ckharris@vims.edu
Marjorie Friedrichs, Virginia Institute of Marine Science, College of William & Mary Hayes Virginia, United States. marjy@vims.edu
Abstract:
Transport of particulate organic matter within and through coastal marine environments depends on the relative effects of supply, storage in the seabed, subsequent resuspension, and advection within the water column, as well as biogeochemical reactions. These transport processes are often invoked to explain spatial or temporal variations in biogeochemical fluxes, but the extent to which resuspension and advection affect water-column biogeochemistry and carbon remineralization is debated and can be challenging to measure. A modeling approach promises a means of quantifying these fluxes for a range of conditions, and enables extrapolation beyond point observations. Typically, however, water column biogeochemistry models have used simplifying assumptions to represent benthic boundary conditions, and have neglected resuspension and subsequent advection of particulate organic matter and nutrients. Yet, sensitivity tests have shown that estimates of biogeochemical cycling in dynamic coastal environments are sensitive to how sediment processes are represented in models.
To evaluate the role of seabed resuspension and subsequent advection on biogeochemical fluxes, we developed a coupled model within the Regional Ocean Modeling System (ROMS) framework. The coupled model includes hydrodynamic, sediment transport, and biogeochemical processes. To link the sediment transport and water column biogeochemical modules, a diagenetic model was added to the seabed. The coupled model accounts for processes including advection, resuspension, diffusion within the seabed and at the sediment-water interface, and organic matter remineralization. Here, we implemented coupling between hydrodynamics, sediment transport, and a biogeochemical model within a full three-dimensional numerical model to investigate the relative effects of supply, resuspension, and advection on biogeochemical fluxes within the riverine-influenced Gulf of Mexico. Preliminary results indicate that seabed and bottom boundary layer oxygen consumption increased where and when particulate organic carbon accumulates on the shelf. Ongoing work includes analyzing results for nitrogen fluxes and from time-periods with low-oxygen conditions.
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